Just wanted to add, from both personal experience and warnings of others, that if you dismantle a hard drive you should watch out for how powerful the magnets are. I doubt there is anything to worry about unless you purposely play with the magnets. They are powerful enough that I could not pull them apart with my hands. They could easily pinch you or hurt you badly if they were to slam together.
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XonatronNov 5 '12 at 14:57

5 Answers
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Physical destruction of a drive is tricky business. There are many companies that deal specifically in the field of data destruction, so if you are doing any kind of mass you may want to at least look at their price list. If you contract, make sure the company is properly bonded/insured, and provides audit trails for each destroyed item. In the worst case scenario that your information does get out, you want the document in hand that says your contractor properly destroyed the item in question. Then, at least, you can transfer the liability.

When it comes to drive destruction you typically see one of two main fields:

Disk Degaussing

Physical Destruction

Degaussing

Degaussing used to be the norm, but I am not such a big fan. On the plus side it is fast, you'll normally just dump the disks on a conveyor belt and watch them get fed through the device. The problem is auditability. Since the circuitry is rendered wobbly, you won't be able to do a spot check of the drives and verify that the data is gone. It is possible, with some level of probability unknown to me, that data could still exist on the platters. Retrieving the data would, without question, be difficult, but the fact still remains that you cannot demonstrate the data is actually gone. As such, most companies now will actually be doing physical destruction.

Physical Destruction

At the low end, say a small box of drives at a time, you'll have hard drive crushers. They're often pneumatic presses that deform the platters beyond useful recognition. At the risk of supporting a specific product, I have personally used this product from eDR. It works well, and is very cathartic.

At a larger scale, say dozens or hundreds of disks, you'll find large industrial shredders. They operate just like a paper shredder, but are designed to process much stiffer equipment. The mangled bits of metal that are left over are barely identifiable as hard drives.

At an even larger scale you can start looking at incinerators that will melt the drives down to unidentifiable lumps of slag. Since most electronics can produce some rather scary fumes and airborne particulates, I would not recommend doing this on you own. No, this is not a good use of your chiminea.

Manual Dis-assembly

If you are dealing with one or two drives at a time, then simple dis-assembly might be sufficient. Most drives these days are largely held together with torx screws, and will come apart with varying levels of difficulty. Simply remove the top cover, remove the platters from the central spindle. Taking a pocket knife, nail file, screwdriver, whatever, have fun scoring both surfaces of each platter. Then dispose of the materials appropriately. I cannot speak to how recoverable the data is afterwards, but it is probably sufficient. The biggest thing to keep in mind is that while most desktop hard drive platters are metal, some are glass. The glass ones shatter quite extravagantly.

You should also take care of removing and destroying the memory chips on the board because of cache memory and (with "hybrid" drives) of NAND chips containing up to 4GB of cached data.
A good way to do that is to wrap the board in linen or another coarse cloth and hammer it, that should keep broken parts from flying everywhere.

Additional Considerations

Before you decide on a destruction method, make sure to identify what kind of data is stored on each device and treat it appropriately. There may be regulatory or legal requirements for information disposal depending on what data is stored on the disk. As an example, see section 8-306 of DoD 5220.22-M.

All that being said, performing a single pass zero wipe is probably sufficient for your purposes. Modern research indicates that modern hard drives are largely immune to the "magnetic memory" problem we used to see on magnetic tape. I would never bother doing anything more on a household drive unless the drive itself was exhibiting failures.

Wow. Thank you for all of this information. You went above and beyond on this one, covering all bases, but thank you for this. I like how you mention the kind of data and how it matters. I will now have this in mind the next time this matters. EDIT: I would vote you up if I had permission.
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XonatronFeb 2 '12 at 15:26

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@MatthewDoucette Answer acceptance is worth a bit more than an up-vote, although when you have permission you can indeed do both.
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IsziFeb 2 '12 at 19:25

@Iszi, thanks. I now have permission and have done both! :)
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XonatronFeb 2 '12 at 19:27

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+1 for dis-assembly; I think this is the most appropriate and clean method for dealing with a single drive.
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JYeltonFeb 3 '12 at 16:16

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If the 'manual disassembly' method is good enough for your application, don't throw out your hard drive parts! That is good, extremely high-quality metal there, there is no reason to let it go to waste. There is an infinity of things you can do with hard drive parts after you take the drives apart. They have some super-slick bearings, a super-flat and shiny platter, a small-yet-powerful motor for the platter, a linear actuator, and really great case that can be used for a number of craft projects. Surely you can do something with it?
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AJMansfieldOct 16 '13 at 23:52

Your hard drive will undoubtedly contain toxic substances which if heated or burned will be released into the air, not a good thing. If you did this in your oven you would never want to use your oven for food again!

Much better to take the entire drive as is and simply chop it into many pieces. A sheet metal shear should be able to slice through it like butter. Any good machine shop should have one.
Alternatively if you know a fireman have them use the jaws of life on it; those things will cut through almost anything.

Once your drive is transformed into 10-20 little pieces you should have little worry that anyone will get data off it again.

These things shatter and send shrapnel flying around when you cut them. I experienced that first handed.
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Lucas KauffmanFeb 2 '12 at 15:10

Lucas: Of course one wants to use appropriate safety precautions with any machine tool like eye protection, safety shields etc. You will note that I suggested he take it to someone rather than simply whacking it with an ax on a stump ;-)
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JonnyBoatsFeb 2 '12 at 15:17

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I have had some success bending the disks until the coating flakes off - just for fun, not really a useful method at work:-)
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Rory Alsop♦Feb 2 '12 at 16:16

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@RoryAlsop: I'll do that sometimes to, but you do need to be careful with the platters. Most desktop drives are metal, and will bend. Some, and almost if not all laptops drives, are glass. They will make a godawful mess in your lab. Let me tell you. :-/
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Scott PackFeb 2 '12 at 16:57

OT Nitpick: While they're overkill for the materials a hard drive is built out of the Jaws of Life can't cut through anything. In fact the frames of many newer cars are made of steel too strong for first generation jaws to cut through.
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Dan NeelyFeb 2 '12 at 17:01

I have access to a stove used for heating a home, perhaps if I just placed the platers (is that what they are called?) in and burned only those, that might be more safe. What do you think?
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XonatronFeb 2 '12 at 14:51

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I don't know I think killing it with fire is better.
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Lucas KauffmanFeb 2 '12 at 15:06

Alternately, you can pack it full of Sucrose and Potassium Nitrate, which will burn hotter and faster. Just dry mix 35% sugar with 65% stump remover (by mass; experimentation shows this is approximately 1:1 by volume), pour the powdered mixture all over the drive parts, and light it on fire.
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AJMansfieldOct 17 '13 at 14:08

Thanks for this suggestion. Really all are welcome for future reference. (Currently I have drives that I do not wish to even hook up to my computer and go through all that hassle that I wish to destroy, so I'll likely resort to more physical solutions!)
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XonatronFeb 6 '12 at 13:18